1. Field of the Invention
The present invention relates generally to fluid filters; more particularly to pre-septic tank fluid filters; and, still more particularly to filters for the output of washing machines.
2. Description of the Prior Art
The need for pre-septic tank filtration was broadly recognized in the prior art. This need arises particularly due to the fact that contaminated groundwater, that is well water, has been the cause of approximately half of the water-borne disease outbreaks in the United States since approximately 1920. The majority of these outbreaks were known to be caused by pathogenic microorganisms. The United States Environmental Protection Agency has found that failed septic systems are the most frequently-reported cause of groundwater contamination. One out of every four households in the United States is on a septic system, according to the 1990 census bureau, and these households generate over one trillion gallons of waste water every year.
Over 100 disease-causing viruses are known which can be introduced into water supplies through failed septic systems. The effects of these viruses may range from intestinal upset to severe respiratory and central nervous system disorders, as well as death. A properly operating septic system will treat and destroy these dangerous contaminants before they can be introduced to the groundwater supplies. However, a septic system can begin to lose its efficacy in the treatment of disease-carrying effluent in as little as three years.
Once a septic system fails to treat raw sewage, not only the immediate groundwater supplies, but also the surrounding soil will become contaminated. It is possible for homes and entire neighborhoods, particularly lakeshore properties, to lose by far the greater part of their value because of contamination from failed septic systems.
With increasing recognition of this groundwater contamination problem, several states have begun to enact strict laws governing septic systems, and the United States Congress is reviewing the 1994 Clean Water Act with a view to a new focus on home septic systems.
It has been generally believed in the prior art that clothes washing machines are a leading cause of septic failure, even in well-maintained septic systems, and it was generally believed that this was because of the large amount of water used by such machines. However, a five and one-half year research study conducted by the inventor of the present invention on the effects of washing machine discharge on septic systems altered the prior art general knowledge by revealing previously unknown facts, including the facts that: A huge amount of material fibers, that is lint, are being discharged by washing machines; and, this discharge includes a large number of synthetic fibers.
It has been found that an average household will introduce over 250 square feet of lint into their septic system through their washing machine alone, each year. Prior art lint screens and nylon socks trap less than 5% of this debris. This lint, or material fibers, enters the septic system dispersion field and plugs the pores of the soil bed. Further, the problem is compounded because much of the clothing being washed by the machines is made of synthetic materials, such as polyester, nylon, and the like. The abovementioned study has found that septic systems will not break down synthetic substances, and that once these contaminants enter the septic system there is no reasonable way to remove them.
During the above-described research study, data was complied over a five and one-half year test period. Tests were conducted in residential settings with households ranging from two to six occupants using standard washing machines. It was discovered that laundering habits and materials were strikingly similar in all test households. It was found that Saturdays and Sundays were the heaviest wash load days of the week, and as many as 12 wash loads were done in one day. The months of May through October saw the heaviest non-stop usage of the washing machines during these weekends. Over 80% of wash loads were done on full load settings using from approximately 47 to 62 gallons for a complete cycle. Discharge rates from the washing machines averaged 17 to 19 gallons per minute.
By using a 30 micron filter, it was possible to ascertain the types and amounts of solids being discharged from the machines. The amount of solids varied with the types of material being washed, however, the average solid discharge, based on one-week cycles, was 62.60 square inches per wash load. This is a significantly larger amount than was previously assumed by the prior art. Assuming that each wash discharges 60 gallons of water including an amount of solids equal to 62.60 square inches, the annual load on a septic system from just one such washing machine would amount to 37,440 gallons of water and 260 square feet of solids.
The contaminant solids are comprised of 91% organic and non-organic material fibers, that is lint. The remainder of the solids generally comprises approximately 7% hair or pet fur and 2% miscellaneous debris such as sand, clay and the like. Conventional prior art lint screens and nylon socks remove less than 5% of these contaminants. The majority of the material fibers found in the contaminant solids measured one-eighth inch or less. The percentage of synthetics ranged from 20% to over 70% per wash load. Further, it was found that once introduced into the septic tank over 80% of these materials remained in suspension and were flushed out into the drain field from the septic system where an undesirable phenomenon was observed. These minute particles tended to congregate in common areas. These fibers would interlock, forming a mat-like barrier which plugged the pores of the gravel and soil bed. An analysis of failed septic systems shows that they contain large pockets of these mat-like barriers from contaminants throughout the drain field. It was also found that these materials were a leading cause of sewer pipe restrictions and obstructions. Lint would attach itself to grease and/or fats in the pipe creating a dam effect that would, in turn, trap additional grease or fats. This cycle continues to eventually cause a total obstruction of the pipe.
Though a normal septic system will break down organic fibers, such as cotton and wool fibers, in a reasonable period of time, it has been found that due to the lack of ultraviolet light, the septic system does not operate to break down the synthetic fibers. Such synthetic fibers have been shown to be existent in the septic system for periods of greater than 20 years without breaking down. This fact makes obvious the value of preventing the synthetic fibers from entering the septic system, that is, pre-filtering the liquid which carries the synthetics into the system. As stated above, prior art pre-septic filtering systems, including washing machine filters, do not in general remove a sufficiently high percentage of the lint and other debris which carries synthetic fibers into the septic system.